It can be, yes. It can also be perfectly safe.
Inhaling airborne asbestos fibers can cause cancer, and it doesn’t take years of exposure (such as working in mines or factories processing asbestos) to develop problems from asbestos. Inhaling airborne asbestos fibers is a significant, major health risk, so yes, asbestos can ve a very dangerous material, which is why it’s no longer used in building materials.
Asbestos siding itself, though, is rarely dangerous. If it’s intact and installed on exterior walls, it’s perfectly safe, and will remain so for decades and decades. It is only dangerous if the siding is broken into many small pieces, sawed, drilled, etc. Asbestos shingles are perfectly safe to handle, touch, and be in the presence of as long as they are intact and unbroken.